On existing aircraft, engines such as dual-flow dual-body turbojet engines are suspended beneath the wing system by complex mounting systems referred to as engine mounting structures (EMS) or mounting pylons. The mounting pylons normally used have a rigid structure referred to as the primary structure. This primary structure usually forms a box, i.e. it is formed by assembling lower and upper longerons connected together by a plurality of stiffening transverse ribs positioned inside the box. The longerons are arranged on the lower and upper faces, while the side panels close the lateral faces of the box.
In a known manner, the primary structure of these pylons is designed to enable the static and dynamic forces generated by the engines—such as weight, thrust and other dynamic forces—to be transmitted to the wing structure.
In the solutions known in the prior art, the transmission of forces between the engine and the primary structure is conventionally ensured using mounting means comprising a front engine attachment, a rear engine attachment and a thrust spreading device. These elements together form an isostatic attachment system comprising primary attachments to cover nominal operating conditions and secondary attachments to cover operation in the event of failures/faults, also referred to as failsafe cases.
Normally, the rear engine attachment links the primary structure to the exhaust casing of the engine, also referred to as the gas exhaust casing, which is located at the rear end of this engine. A conventional example embodiment of the rear engine attachment is shown in FIG. 1 and disclosed in patent application FR 3 014 841.
This rear engine attachment 7a therefore links the exhaust casing of the engine to the primary structure 6 of the box-shaped mounting pylon. To do so, the attachment 7a comprises a body 100 and a plurality of connecting rods 102 articulated with the engine attachment body 100 and with the clevises on the exhaust casing. More specifically, the body 100 has one or more cross members 104, 106 stacked vertically. The three connecting rods 102 are spaced out transversally, which results in the overall width of the rear engine attachment being relatively large.
It has recently been proposed to install the rear engine attachment level with the inter-turbine casing of the engine, with a view to reducing the deformations of this latter. Limiting such deformations helps to better control blade-tip clearance in high- and low-pressure turbines, and helps to improve overall performance of the engine. Indeed, the fact of moving the rear engine attachment forwards from the exhaust casing towards the inter-turbine casing makes it possible to arrange this attachment in a zone in which the inner aerodynamic fairings of the nacelle, or inner fixed structure (IFS), are wider and therefore facilitate better aerodynamic integration.
However, for this type of installation on the inter-turbine casing, the rear engine attachment usually has a design similar to the one shown in FIG. 1. Consequently, the significant width of same is liable to require the overdimensioning of one or more of the structures inside the nacelle flow path, some of which are intended to streamline the rear engine attachment. Such overdimensioning increases the size of the rear attachment or rear mount fairing (RMF), which may take the form of local enlargements around the two lateral ends of the rear engine attachment, causing aerodynamic disturbances that have an adverse effect on the overall performance of the engine.